Spoon the condensed milk into the base of a small heatproof glass.
Add a strip of lemon peel and pour the liqueur gently over the back of a bar spoon so it sits above the milk.
Pull an espresso and pour it slowly down the spoon to form the third layer.
Top with hot foamed milk.
Dust with cinnamon and serve without stirring — the layers are the point until the drinker breaks them.
Native to Tenerife, where ordering one "completo" gets you all four layers plus the lemon and cinnamon. The lemon peel is not garnish: it sits in the liqueur layer and perfumes it from below.
My Bar Shelf läser ditt skåp och visar varje cocktail du kan göra av det du redan har - inklusive Barraquito.